Olive oil production is a traditional industry originating in the Mediterranean and known since as early as 3,000 B.C. In recent years, the olive oil market has been growing dramatically. The increasing interest in olive oil stems from both its unique rich taste and its health benefits and coincides with the growing public awareness to health food, as well as with the general increasing interest in gourmet food. Indeed, olive oil is considered by many to be superior to other vegetable oils. However, olive oil is also one of the most adulterated agricultural products. Customers are therefore becoming increasingly aware of the possibility that oil distributed as high quality olive oil is actually adulterated oil mixed with, or even consists almost entirely of inferior oils of lower cost. The awareness to health food products, as well as to their freshness and authenticity, has brought with it a new trend of small scale production of basic food products (e.g. bread) for self consumption at home or in small food establishments such as restaurants, delicatessen and specialized boutiques. In accordance with this trend, small scale appliances, sized to be placed on a kitchen counter, such as bread machine, home-use coffee roasting device, etc., are now gaining popularity. With respect to olive oil, recent years show an increasing number of olive oil boutiques which specialize in production of high quality oil by careful selection of olives and a close control over production. A household countertop cold press machine for producing small quantities of olive oil designed by the inventors of the present invention is described in international publication WO2010/007610.
The oil in olives is accumulated in the mesocarp cells, mostly in the vacuoles and to a smaller extent in the cytoplasm. The first stage in the process of olive oil extraction from whole olives is to crush or grind the olives into an olive paste (mash), which contains both broken olive pits (stones) and mashed flesh. Typically, crushing or grinding is followed by malaxation (slow mixing) of the paste to facilitate breaking of the oil-containing cells to release the oil and to allow coalescence of the oil droplets and separation of the liquids from the solids. The sharp stone particles present in the paste facilitate the breaking of the cellular material. The liquid, which contains both oil and vegetation water, is then extracted from the paste by applying pressure or centrifugation. Depending on the specific method and equipment, the separation of the paste into liquid and solid and the separation of the liquid into oil and water may be performed sequentially (two-phase separation) or concurrently (three-phase-separation)
The present invention focuses on the first step of the olive oil production, namely the preparation of the olive paste from whole olives.
The olive stone (pit) has an exceptionally rigid structure. Invoking the initial collapse/breakage of the stone requires a certain critical force, while further breakage of the initial fragments into smaller ones requires forces of an order of magnitude smaller. The critical force may be of up to, or even more than, about 40 kg, depending on the stone's size.
Traditionally, olive paste was prepared by millstones. Nowadays, modern olive oil plants commonly use a hammer mill which operates at high rotational speeds to impact the olives, tear their flesh and break their stones. Although, the use of hammer mills is advantageous over traditional millstones with respect to capacity, efficiency and costs, it does affect the quality of the olive oil. Because of the high rotational speed of the hammers, the impact results in overheating of the processed olives and even more significantly, in a transient high increase of the local temperature at the impact's site, which might even reach a temperature as high as boiling temperature. The overheating has certain disadvantages with respect to the oil quality and might compromise its health beneficial and organoleptic properties. Indeed, it is believed that olive oil prepared by modern technology is somewhat inferior to oil produced by traditional techniques where the processing is much slower.
It is one object of the invention to provide method and device for processing olives into a paste which overcome the above drawbacks and which can be implemented in, but are not limited to, a small-scale countertop home appliance.
It is another object of the invention to provide a method and device for crushing/grinding aggregate material, such as olives, which are low speed and low torque, therefore preventing overheating and maintaining low temperatures throughout the olive oil processing.
Other advantages of the present invention will become apparent from the following description.